In hybrid optical systems, individual optical components, typically semiconductor based, are disposed on a single substrate and placed in optical communication with other such components to collectively perform one or more optical functions. Such hybrid systems allow the system designer the flexibility to select optimal materials/technology for each component of the hybrid system.
Hybrid systems often combine III-V semiconductors, desirable as light emitters and active optics (i.e., modulators and detectors), with silicon. In particular, since silicon is readily and precisely micromachinable, it is useful as a support for providing accurate and stable alignment of III-V devices or other components. In addition to its utility as a physical support, silicon provides electronics capabilities, and is useful for forming and/or supporting passive optics (e.g., waveguides, etc.). Used in such a manner, silicon serves as an "optical bench." Optical devices, systems and technology implemented in this manner are conventionally referred to as silicon optical bench (SiOB) devices, etc.
A switching function is often required in SiOB systems. Conventionally, the switching function has been provided using a Mach Zehnder interferometer. The interferometer splits an optical signal into two signals that traverse different optical paths through two waveguide arms. Once separated in that manner, a relative phase shift is, or is not, induced between the two signals. The two signals are then reunited. In the absence of a phase shift, the signals constructively interfere resulting in a maximum output intensity. When an appropriate phase shift (i.e., .pi.) is imparted, destructive interference results, providing a substantial attenuation of the original signal. Thus, an "on-off" function is provided.
Unfortunately, such interferometric switches suffer several drawbacks or limitations, including the polarization dependence of phase modulation, insertion losses, electroabsorption effects and parasitic interference between the two waveguide arms. As such, the art would benefit from a device capable of providing a switching capability to a SiOB device that avoids many of the performance limitations of interferometric switches.